Enhanced condensation heat-transfer tube

ABSTRACT

This invention provides an enhanced condensation heat-transfer tube, which is furnished with spiral fins on the outer surface. Axial spacing between the said fins regularly changes in width. In a preferred embodiment, the said fins regularly change in height along the axle. Such spiral fins with even changes in height and spacing change the surface tension of the condensate membrane between the fins outside of the tube, so as to enhance the “Gregorig” effect (average heat resistance reduces due to uneven thickness of condensate membranes). In this way, it further strengthens condensation heat transfer effects outside of the tube. At the same time, it accelerates flowing of the condensate to the bottom, enhances heat transfer effect, and improves the tube bundle effect.

BACKGROUND

1. The Field of the Present Disclosure

This invention involves the technical field of heat-transfer tubes, especially a type of enhanced condensation heat-transfer tube.

2. Description of Related Art

With the concept of energy conservation and high efficiency being widely promoted, requirements for heat transfer performance in condenser design has gradually increased and a highly-efficient heat-transfer tube is the key factor affecting the heat transfer performance of a condenser. A Chinese patent document, with publication number of CN1982829A, discloses a type of copper heat-transfer tube with triangular smooth fins on the outside. Such smooth fins increase the heat transfer area. When used in a condenser, it reduces condensate membrane and accelerates condensate dripping. Thus, it is of higher heat transfer efficiency than a smooth tube. However, a smooth fin easily enables “bypass” of condensate and renders the condensate to flow less smoothly. As a result, condensation thermal resistance of the fins increases and the heat transfer efficiency is reduced. Another Chinese patent document, with the publication number CN101813433A, discloses another type of heat-transfer tube, for which a top slotted fin structure is adopted. Its serration structure may pierce through the condensate membrane and the fin platform can enhance condensation heat transfer performance to a certain extent.

Structures of the said heat-transfer tube of condensers in current use are shown in FIG. 1 and FIG. 2 (FIG. 3 shows the front-view projection). Fins are distributed on the surface of the heat-transfer tube body, which improves the heat transfer performance on the condensation side to a certain extent. However, as the fins are of the same height and spacing and are evenly distributed, surface tension of the condensate cannot be put into full use to improve heat transfer performance. As a result, the heat transfer efficiency of the heat-transfer tube is relatively low, failing to fully meet the optimal requirements of refrigerating equipment for heat transfer performance of condensers.

The features and advantages of the present disclosure will be set forth in the description which follows, and in pal will be apparent from the description, or may be learned by the practice of the present disclosure without undue experimentation. The features and advantages of the present disclosure my be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the disclosure will become apparent from a consideration of the subsequent detailed description presented in connection with the accompanying drawings in which:

FIG. 1 is the structural diagram 1 of an enhanced condensation heat-transfer tube in current use;

FIG. 2 is the structural diagram 2 of an enhanced condensation heat-transfer tube in current use;

FIG. 3 shows the front view of an enhanced condensation heat-transfer tube in current use;

FIG. 4 shows a front view of the first embodiment of the enhanced condensation heat-transfer tube as described in this invention;

FIG. 5 shows a front view of the second embodiment of the enhanced condensation heat-transfer tube as described in this invention;

FIG. 6 shows a front view of the third embodiment of the enhanced condensation heat-transfer tube as described in this invention;

FIG. 7 shows a front view of the fourth embodiment of the enhanced condensation heat-transfer tube as described in this invention;

FIG. 8 shows a front view of the fifth embodiment of the enhanced condensation heat-transfer tube as described in this invention;

FIG. 9 shows a front view of the sixth embodiment of the enhanced condensation heat-transfer tube as described in this invention;

FIG. 10 shows a front view of the seventh embodiment of the enhanced condensation heat-transfer tube as described in this invention

DETAILED DESCRIPTION

This invention solves the technical problem of low efficient heat transfer performance by providing an enhanced condensation heat-transfer tube with improved heat transfer performance.

To solve the above problems, the present invention discloses a type of enhanced condensation heat-transfer tube, which is furnished with spiral fins on the outer surface and features regular changes in axial direction and in the width of spacing between the said fins.

In preferred embodiments, for the said spiral fins, smooth fins are used; or slotted fins, formed by grooving on the top or both sides of smooth fins, are used.

In preferred embodiments, 26 to 60 of said spiral fins are arranged every inch along the axle and the axial spacing between the fins ranges from 0.4 to 1 mm.

In preferred embodiments, spacing between the said fins changes along the axle with alternating wide spacing and narrow spacing; or spacing between the said fins changes along the axle with alternating one wide spacing and two narrow spacing; or spacing between the said fins changes along the axle with alternating two wide spacing and one narrow spacing.

In preferred embodiments, the height of the said spiral fins regularly changes in the axial direction.

in preferred embodiments, the said spiral fins are 0.1 to 0.4 mm thick with their heights ranging from 0.4 to 1.5 mm.

In preferred embodiments, the height of the said spiral fins regularly changes along the axle with alternating one high fin and one short fin; or the height of the said spiral fins regularly changes along the axle with alternating one high fin and two short fins; or the height of the said spiral fins regularly changes along the axle with alternating two high fins and one short fin.

In preferred embodiments, the helical angle of the said spiral fins ranges from 0.3° to 1.5°.

In preferred embodiments, a threaded ridge is provided on the inner surface of the said heat-transfer tube.

In preferred embodiments, the angle between the said threaded ridge and the axle ranges from 30° to 60°; there are 6 to 60 internal threads on the threaded ridge, with heights ranging from 0.1 to 0.6 mm.

Compared to existing technologies, this invention is advantageous in the following aspects:

The preferred embodiments of this invention disclose that the spacing between the fins on the outside surface of the enhanced condensation heat-transfer tube and the height of the fins vary. Surface tension of the condensate changing evenly can be put into full utilization to reduce the thickness of the condensate membrane. Uneven distribution of thickness in condensate membranes may reduce average heat resistance and enhance the “Gregorig” effect, so as to increase the coefficient of heat transfer on the outer surface of the heat-transfer tube. At the same time, even changes in surface tension and variation of the curvature reduce the retention of the condensate and accelerate its dripping so as to improve heat transfer performance and mitigate the “tube bundle effect”. Heat transfer efficiency inside and outside of the tube provides optimal combination to increase the overall heat transfer efficiency of the enhanced condensation heat-transfer tube.

Reference FIG. 4 shows a front-view projection of the first embodiment of the enhanced condensation heat-transfer tube described in this invention. In this preferred embodiment, there are spiral fins on the outer surface of the heat-transfer tube and spacing between the fins varies regularly along the axle with alternating wide and narrow spacing. in this embodiment, 26-60 spiral fins are arranged per inch along the axle, with axial spacing of 0.4-1 mm. The fins are 0.1 to 0.4 mm thick, with a helical angle of 0.3° to 1.5° and a height of 0.4 to 1.5 mm. In addition, the spiral fins can be smooth fins or slotted fins formed by grooving on the top or on both sides of the smooth fins. As spacing between the fins varies regularly, fins of such structure enable an even change in the surface tension of the condensate between fins as well as an even change in the thickness of condensate membrane correspondingly. It may reduce average heat resistance and enhance the “Gregorig” effect to improve the coefficient of heat transfer on the outer surface of the heat-transfer tube. At the same time, even changes in surface tension and surface curvature reduce retention of condensate between fins and enables the condensate to flow and drip quickly to the bottom of the fins, so as to improve condensation heat transfer performance and mitigate the “tube bundle effect”. Fins of such structure can be formed by intrusion using a combination of tools, without increasing metal consumption.

Reference FIG. 5 shows a front-view projection of the second embodiment of the enhanced condensation heat-transfer tube described in this invention. In this preferred embodiment, the spacing between fins varies regularly with alternating one wide spacing and two narrow spacings. The rest are the same as those in the first embodiment.

Reference FIG. 6 shows a front-view projection of the third embodiment of the enhanced condensation heat-transfer tube described in this invention. In this preferred embodiment, the spacing between fins varies regularly with alternating two wide spacing and one narrow spacings. The rest are the same as those in the first embodiment.

Reference FIG. 7 shows a front-view projection of the fourth embodiment of the enhanced condensation heat-transfer tube described in this invention. In this preferred embodiment, there are fins on the outer surface of the heat-transfer tube with their height varying regularly along the axle with alternating one high fin and one short fin. In this embodiment, shod fins are 0.4 to 1.0 mm high, white high fins are 0.6 to it 1.5 mm high. Fins of such structure enable even change in the surface tension of the condensate between fins. Correspondingly, thickness of the condensate membrane varies evenly in order to reduce average heat resistance and enhance the “Gregorig” effect to improve the coefficient of heat transfer on the outer surface of the heat-transfer tube. At the same time, even changes in surface tension and surface curvature reduce retention of condensate between fins and enable the condensate to flow and drip quickly to the bottom of the fins, so as to improve condensation heat transfer performance and mitigate the “tube bundle effect”. Fins of such structure can be formed by intrusion using a combination of tools, without increasing metal consumption.

Reference FIG. 8 shows a front-view projection of the fifth embodiment of the enhanced condensation heat-transfer tube described in this invention. In this preferred embodiment, fins are arranged at such height varying regularly with alternating one high fin and two short fins. The rest are the same as those in the fourth embodiment.

Reference FIG. 9 shows a front-view projection of the sixth embodiment of the enhanced condensation heat-transfer tube described in this invention. In this preferred embodiment, fins are arranged at such height varying regularly with alternating two high fins and one short fin. The rest are the same as those in the fourth embodiment.

The above embodiments of this invention can be combined to have different shapes of fins with their spacing and height varying.

In addition, in the above preferred embodiments of this invention, dedicated equipment can be used to acquire a threaded ridge 1 in the tube so as to improve the coefficient of heat transfer in the tube. The angle between the threaded ridge 1 and the axle is from 30° to 60°; there are 6 to 60 internal threads, and the ridges are 0.1 to 0.6 mm high. Threaded ridge 1 may damage the boundary of the fluid in the tube and increase disturbance to fluid in the tube, so as to enhance heat transfer and improve the coefficient of heat transfer in the tube.

Reference FIG. 10 shows a structural diagram of the seventh embodiment of the enhanced condensation heat-transfer tube described in this invention. In this preferred embodiment, the height of the fins varies regularly in the axial direction with alternating one high tin and one low fin. At the same time, spacing between fins varies regularly along the axle with alternating one wide spacing and one narrow spacing.

The specific structure of the enhanced heat-transfer tube for condenser as described in this invention will be introduced in the following in combination with specific embodiments:

When the enhanced condensation heat-transfer tube described in this invention is processed and manufactured as per the structure shown in FIG. 10, copper, copper alloy, or other metal materials can be used for the tube body. The tube will have an outer diameter of 19 mm and wail thickness of 1.13 mm. Specialized tube milling and metal spinning methods will be adopted for simultaneous and integrated processing of the outer and inner of the tubesurface. Spiral fins will be processed along the circumference direction on the outer surface of the tube body. Fins will be spaced at d1 of 0.53 mm or d2 of 0.61 mm and have a height h1 of 0.75 mm or h2 of 0.9 mm. The top of the fins will be grooved with slots by roll pressing and 120 slots will be provided along the circumference direction.

In addition, dedicated equipment will be used to process a threaded ridge 1 on the inner surface of the tube to improve the coefficient of heat transfer outside and inside the tube. In the seventh embodiment of this invention, the threaded ridge 1 is 0.38 mm high, the angle between the ridge and the axle is 42°, and there are 45 threads.

According to statistics obtained from actually measured data, when refrigerant R134a is used, the condensation heat transfer performance of this invention is 12% higher compared with existing technologies.

In the above embodiments of this invention, considering the heat transfer performance and cost performance of metal materials, copper is preferred to make this condensation heat-transfer tube. Other metal materials such as copper alloy, aluminum, aluminum alloy, low carbon steel, and copper and aluminum composite can also be used.

All embodiments in this Specification are described in a progressive manner. Description of each embodiment is emphasized on its difference from other embodiments and reference can be made to each other for the identical and similar parts of the embodiments.

This summary introduces in detail a type of enhanced condensation heat-transfer tube provided in this invention. It elaborates the principles and implementation methods of this invention through specific examples. Description of the above embodiments is merely used to help understand the core idea of this invention. At the same time, common technicians in this field may change the specific embodiment methods and application scope in line with the idea of this invention. To sum up, the contents of this Specification shall not be construed as the limit to this invention. 

1. An heat-transfer tube for enhanced condensation, comprising a tube Body, and outer spiral fins integrated on outer surface of the tube body wherein the spiral fins are featured by regular changes in axial direction and in the width of spacing between the said fins.
 2. The heat-transfer tube according to claim 1, wherein said spiral fins having smooth surface; or said spiral fins being slotted fins by grooving the smooth fin on the top or on both rides.
 3. The heat-transfer tube according to Claim 1, wherein 26 to 60 of said spiral tins are provided in every inch along the axial direction of the outer surface of the tube body and the spiral fins are axially spaced 0.4 to 1 mm.
 4. The heat-transfer tube according to claim 1, wherein the spacing between fins regularly changes in the axial direction with alternating wide and narrow spacing; or the spacing between fins regularly changes in the axial direction with alternating wide spacing and two narrow spacings; or the spacing between fins regularly changes in the axiai direction with alternating two wide spacings and one narrow spacing.
 5. The heat-transfer tube ncording to claim 1, wherein said spiral fins have regular changes in the height of the said spiral fins in the axial direction.
 6. The heat-transfer tube according to claim 5, wherein said spiral fins are 0.1 to 0.4 mm thick, with their height ranging between 0.4 to 1.5 mm.
 7. The heat-transfer tube according to claim 5, is featured by the following: the height of the said spiral fins regularly changes along the axial direction with alternating one high fin and one short fin; or the height of the said spiral fins regularly changes along the axial direction with alternating one high fin and two short fins; or the height of the said spiral fins regularly changes along the axial direction with alternating two high fins and one short fin.
 8. The heat-transfer tube according to claim 1, is featured by that the helical angle of the said spiral fins ranges from 0.3° to 1.5°.
 9. The heat-transfer tube according to claim 1, wherein threaded ridges are furnished on the inner surface of the said heat-transfer tube.
 10. The heat-transfer tube according to claim 9, wherein the said threaded ridges are angled between the threaded ridge and the axle ranging from 30° to 60°; said threaded ridge has 6 to 60 internal threads, with their height ranging from 0.1 o 0.6 mm.
 11. The heat-transter tube according to claim 5, wherein threaded ridges are furnished on the inner surface of the said heat-transfer tube.
 12. The heat-transfer tube according to claim 11, wherein the said threaded ridges are angled between the threaded ridge and the axle ranging from 30° to 60°; said threaded ridge has 6 to 60 internal threads, with their height ranging from 0.1 to 0.6 mm. 